Apparatus for transferring a substrate in a lithography system

ABSTRACT

An apparatus for transferring substrates within a lithography system, the lithography system comprising a substrate preparation unit for clamping a substrate onto a substrate support structure to form a clamped substrate, and an interface with a substrate supply system for receiving unclamped substrates. The apparatus comprises a body provided with a first set of fingers for carrying an unclamped substrate and a second set of fingers for carrying a substrate support structure, and the first set of fingers is located below the second set of fingers, and fingers of the first set of fingers have a different shape than the fingers of the second set of fingers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for transferringsubstrates within a lithography system, the lithography systemcomprising a substrate preparation unit for clamping a substrate onto asubstrate support structure to form a clamped substrate, and aninterface with a substrate supply system for receiving unclampedsubstrates.

2. Description of the Related Art

In the semiconductor industry, an ever increasing desire to manufacturesmaller structures with high accuracy and reliability puts great demandson wafer processing technology. In particular, it is important tomaximize wafer throughput of wafer processing equipment whilemaintaining the lowest capital costs and operational costs, and withoutexcessive use of floor space. Floor space in a semiconductormanufacturing environment is expensive, as most space needs to meet highstandard clean room conditions. Therefore, the floor space that is to beoccupied by wafer processing equipment, i.e. the so-called footprint, ispreferably as limited as possible. Furthermore, to ensure that cleanroom conditions can be maintained, wafer processing equipment ispreferably serviced within the clean room.

A very critical step in the manufacturing of integrated circuits on awafer is lithography. In a lithography process, a predetermined patternis transferred onto a semiconductor substrate, often referred to as awafer. Currently, the smallest dimensions of structures patterned with alithography apparatus are about 70 nm in size. However, to produce evenmore complex circuits, structures of smaller size are desired.

The throughput of lithography systems is also a critical factor. Chargedparticle lithography machines are capable of patterning substrates atextremely small dimensions, but at a lower throughput. Currently,optical lithography machines are available which can pattern about 100wafers per hour. A cluster of 10 charged particle lithography machines,each capable of patterning about 10 wafers per hour, can match thisthroughput.

The efficient delivery of substrates to be exposed to each lithographymachine and retrieval of exposed substrates from each lithographymachine is a critical factor in maximizing throughput of the system as awhole.

BRIEF SUMMARY OF THE INVENTION

The invention to provides according to one aspect, an apparatus fortransferring substrates within a lithography system, the lithographysystem comprising an interface with a substrate supply system forreceiving unclamped substrates and a substrate preparation unit forclamping an unclamped substrate onto a substrate support structure toform a clamped substrate. The apparatus comprises a body provided with afirst set of fingers for carrying an unclamped substrate and a secondset of fingers for carrying a clamped substrate (i.e. a substrate andsubstrate support structure clamped together). The first set of fingersis located below the second set of fingers, and fingers of the first setof fingers have a different shape than the fingers of the second set offingers.

The fingers of the first and second sets of fingers may both extend fromthe body in the same direction. The fingers of the first set of fingersmay be arranged sufficiently below the fingers of the second set offingers so that the fingers of the first set of fingers do not interferewith a substrate support structure carried by the second set of fingers.The apparatus for transferring substrates is thus arranged fortransferring both unclamped substrates which are smaller and lighter andclamped substrates which are larger and heavier (due to the clampedsubstrate including both the substrate and substrate support structure).

The fingers of the first set of fingers may take the form of straight,substantially parallel bars, with a length extending from the body thatexceeds the radius of the unclamped substrate. The fingers of the firstset of fingers may be separated by a distance less than the diameter ofthe unclamped substrate to provide a stable platform to securely liftthe unclamped substrate. The fingers of the second set of fingers maytake the form of opposing crescent structures with a length extendingfrom the body that exceeds the radius of the substrate supportstructure. The fingers of the second set of fingers may be arranged tosurround, at least partially, the substrate support structure, and maybe arranged to engage and hold the substrate support structure at two ormore points around its circumference. The body may be mounted on a robotarm comprising a base moveable in a substantially vertical direction,and one or more sections for movement in a substantially horizontalplane. The base may move upwards and downwards on a vertical rail. Thesections may take the form of jointed arms, the robot arm comprising twojointed arms which may swivel about an axis and extend in a horizontaldirection. The apparatus for transferring substrates may be thusarranged for transferring both unclamped and clamped substrates betweenlocations at different heights, e.g. between an interface, a substratepreparation unit, and a load lock disposed in a vertical stackedarrangement. The base may be arranged for vertical movement within arobot space, and the robot arm may be arranged for transferring bothunclamped and clamped substrates horizontally between the locations atdifferent heights and the robot space to transfer the substrates betweenthe different locations.

The substrate transfer apparatus may further comprise a horizontaltransfer apparatus arranged for transferring unclamped substrates to andfrom the interface. The interface may comprise three or more pins, thepins arranged for vertical movement to lift an unclamped substrate froma first position accessible by the first set of fingers of the substratetransfer apparatus to a second position accessible by the horizontaltransfer apparatus.

According to another aspect the invention provides a load lock transferapparatus for transferring structures onto which substrates have beenclamped within a load lock system in a lithography system unit. Theapparatus comprises a body provided with at least two fingers forcarrying the substrate supporting structure, and the fingers are locatedat different height levels. The fingers may take the form of opposingcrescent structures with a length extending from the body that exceedsthe radius of the substrate support structure. The fingers may bearranged to surround, at least partially, the substrate supportstructure.

Another aspect the invention relates to a lithography system comprisinga lithography apparatus arranged in a vacuum chamber for patterning asubstrate, a load lock system for transferring substrates into and outof the vacuum chamber, a substrate preparation unit for clamping asubstrate onto a substrate support structure to form a clampedsubstrate, an interface with a substrate supply system for receivingunclamped substrates, and a substrate transfer apparatus fortransferring substrates within the lithography system as describedabove. The load lock system may be provided with a load lock transferapparatus for transferring structures onto which substrates have beenclamped as described above, the load lock transfer apparatus arrangedfor receiving substrate support structures from the substrate transferapparatus and placing the substrate support structures into thelithography apparatus, and for removing substrate support structuresfrom the lithography apparatus and giving the substrate supportstructures to the substrate transfer apparatus.

Another aspect the invention relates to a substrate support structurefor carrying a substrate for use in a lithography system, the substratesupport structure comprising a body provided with a surface foraccommodating the substrate, and two protrusions (which may be in theform of lips) positioned along the circumference of the substratesupport structure, wherein the protrusions are located at a first heightlevel above the center of mass of the substrate support structure. Thefirst height level may be above the center of mass of the combination ofthe substrate support structure and a substrate clamped thereon. The twoprotrusions may be located along one side of the substrate supportstructure. The substrate support structure may further comprise afurther protrusion located at the other, opposing, side of the substratesupport structure. This arrangement allows the fingers of the apparatusfor transferring substrates to engage with the protrusions, thusengaging the substrate support structure at three points around itscircumference to carry it securely.

The structure may further comprises three additional protrusions,wherein two of the additional protrusions are provided at the firstheight level between the two protrusions located along the one side ofthe substrate support structure, and the third protrusion of theadditional protrusions may be provided at the other, opposing, side ofthe substrate support structure at a second height level, the secondheight level being lower than the first height level. This arrangementallows the substrate support structure to be carried by the apparatusfor transferring substrates with fingers at different heights, an upperfinger arranged to engage with the protrusions at the first height leveland a lower finger arranged to engage with the third protrusion at thesecond height level. By having the protrusions at different heights anda transfer apparatus with fingers at different heights which match theheight difference of the protrusions, the substrate support structuremay be carried securely while facilitating hand-off of the substratesupport structure between two

Another aspect the invention relates to a method for handing over asubstrate support structure provided with a substrate on a surfacethereof. The substrate support structure comprises a body provided witha surface for accommodating the substrate; two or more first protrusionspositioned around the circumference of the substrate support structure,at least one of the first protrusions being positioned at a first heightlevel above the center of mass of the substrate support structure; andtwo or more second protrusions positioned around the circumference ofthe substrate support structure, at least one of the second protrusionsbeing positioned at a first height level above the center of mass of thesubstrate support structure and at least one of the second protrusionsbeing positioned at a second height level lower than the first heightlevel. The method comprises picking up the substrate support structurewith a substrate transfer apparatus as described above, so that thefingers of the second set of fingers engage with the first protrusions;moving the substrate support structure towards a load lock transferapparatus as described above; moving the substrate transfer apparatus orthe load lock transfer apparatus so that the fingers of the load locktransfer apparatus engage with the second protrusions; and moving thesubstrate transfer apparatus or the load lock transfer apparatus so thatthe fingers of the substrate transfer apparatus disengage from the firstprotrusions; and retracting the substrate transfer apparatus so that thesubstrate support structure is carried by the load lock transferapparatus.

The step of moving the substrate transfer apparatus or the load locktransfer apparatus so that the fingers of the load lock transferapparatus engage with the second protrusions comprises moving thesubstrate transfer apparatus or the load lock transfer apparatus so thatat least one of the fingers of the substrate transfer apparatus and atleast one of the fingers of the load lock transfer apparatus overlapeach other at different heights around the circumference of thesubstrate support structure.

It will be evident that the presently invented principle may be set intopractice in various manners.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the invention will be further explained withreference to embodiments shown in the drawings wherein:

FIG. 1 is a simplified schematic drawing of an embodiment of a chargedparticle lithography apparatus;

FIG. 2 is a simplified block diagram of a modular lithography apparatus;

FIG. 3 a shows a top view of a layout of lithography system;

FIG. 3 b schematically shows a cross-sectional side view of a portion ofthe lithography system of FIG. 3 a;

FIG. 3 c schematically shows a side view of another portion of thelithography system of FIG. 3 a;

FIG. 4 schematically shows a lithography system unit within a clusteredcharged particle lithography system;

FIG. 5 schematically shows an exemplary trajectory of a substratehandling robot in a lithography system unit;

FIG. 6 shows a clustered lithography system;

FIG. 7 shows a portion of the clustered lithography system with itscover removed;

FIGS. 8 a, 8 b show an interface between a substrate transfer system anda preparation system at different stages of substrate transfer;

FIGS. 9 a, 9 b schematically show a carrier according to an embodimentof the invention;

FIG. 10 schematically shows a clamped substrate handling unit for use ina load lock system;

FIG. 11 shows a substrate preparation unit for placement of a substratesupport structure onto which a substrate is to be clamped;

FIG. 12 schematically shows a clamped substrate handling robot for usein a load lock system;

FIG. 13 a shows the transfer of a clamped substrate from a substratepreparation unit towards a load lock system;

FIG. 13 b shows a more detailed view of the load lock system depicted inFIG. 13 a;

FIGS. 14 a, 14 b schematically show the transfer of a processed clampedsubstrate from the load lock system towards a substrate preparationunit; and

FIGS. 15 a, 15 b show two different stages of a replacement of clampedsubstrates within a load lock system.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following is a description of various embodiments of the invention,given by way of example only and with reference to the drawings.

FIG. 1 shows a simplified schematic drawing of an embodiment of acharged particle lithography apparatus 100. Such lithography systems aredescribed for example in U.S. Pat. Nos. 6,897,458 and 6,958,804 and7,019,908 and 7,084,414 and 7,129,502, U.S. patent applicationpublication no. 2007/0064213, and co-pending U.S. patent applicationsSer. Nos. 61/031,573 and 61/031,594 and 61/045,243 and 61/055,839 and61/058,596 and 61/101,682, which are all assigned to the owner of thepresent invention and are all hereby incorporated by reference in theirentirety.

In the embodiment shown in FIG. 1, the lithography apparatus 100comprises an electron source 101 for producing an expanding electronbeam 120. The expanding electron beam 120 is collimated by collimatorlens system 102. The collimated electron beam 121 impinges on anaperture array 103, which blocks part of the beam to create a pluralityof beamlets 122. The system generates a large number of beamlets 122,preferably about 10,000 to 1,000,000 beamlets.

The electron beamlets 122 pass through a condenser lens array 104 whichfocuses the electron beamlets 122 in the plane of a beam blanker array105, comprising a plurality of blankers for deflecting one or more ofthe electron beamlets. The deflected and undeflected electron beamlets123 arrive at beam stop array 108, which has a plurality of apertures.The beamlet blanker array 105 and beam stop array 108 operate togetherto block or let pass the beamlets 123. If beamlet blanker array 105deflects a beamlet, it will not pass through the corresponding aperturein beam stop array 108, but instead will be blocked. But if beamletblanker array 105 does not deflect a beamlet, then it will pass throughthe corresponding aperture in beam stop array 108, and through beamdeflector array 109 and projection lens arrays 110.

Beam deflector array 109 provides for deflection of each beamlet 124 inthe X and/or Y direction, substantially perpendicular to the directionof the undeflected beamlets, to scan the beamlets across the surface oftarget or substrate 130. Next, the beamlets 124 pass through projectionlens arrays 110 and are projected onto substrate 130. The projectionlens arrangement preferably provides a demagnification of about 100 to500 times. The beamlets 124 impinge on the surface of substrate 130positioned on moveable stage 132 for carrying the substrate. Forlithography applications, the substrate usually comprises a waferprovided with a charged-particle sensitive layer or resist layer.

The charged particle lithography apparatus 100 operates in a vacuumenvironment. A vacuum is desired to remove particles which may beionized by the charged particle beams and become attracted to thesource, may dissociate and be deposited onto the machine components, andmay disperse the charged particle beams. A vacuum of at least 10⁻⁶ baris typically required. In order to maintain the vacuum environment, thecharged particle lithography system is located in a vacuum chamber 140.All of the major elements of the lithography apparatus 100 arepreferably housed in a common vacuum chamber, including the chargedparticle source, projector system for projecting the beamlets onto thesubstrate, and the moveable stage.

In an embodiment the charged particle source environment isdifferentially pumped to a considerably higher vacuum of up to 10⁻¹⁰mbar. In such embodiment, the source may be located in a separatechamber, i.e. a source chamber. Pumping down the pressure level in thesource chamber may be performed in the following way. First, the vacuumchamber and the source chamber are pumped down to the level of thevacuum chamber. Then the source chamber is additionally pumped to adesired lower pressure, preferably by means of a chemical getter in amanner known by a skilled person. By using a regenerative, chemical andso-called passive pump like a getter, the pressure level within thesource chamber can be brought to a lower level than the pressure levelin the vacuum chamber without the need of a vacuum turbo pump for thispurpose. The use of a getter avoids the interior or immediate outsidevicinity of the vacuum chamber being submitted to acoustical and/ormechanical vibrations as would be the case if a vacuum turbo pump orsimilar would be used for such a purpose.

FIG. 2 shows a simplified block diagram illustrating the principalelements of a modular lithography apparatus 200. The lithographyapparatus 200 is preferably designed in a modular fashion to permit easeof maintenance. Major subsystems are preferably constructed inself-contained and removable modules, so that they can be removed fromthe lithography apparatus with as little disturbance to other subsystemsas possible. This is particularly advantageous for a lithography machineenclosed in a vacuum chamber, where access to the machine is limited.Thus, a faulty subsystem can be removed and replaced quickly, withoutunnecessarily disconnecting or disturbing other systems.

In the embodiment shown in FIG. 2, these modular subsystems include anillumination optics module 201 including the charged particle beamsource 101 and beam collimating system 102, an aperture array andcondenser lens module 202 including aperture array 103 and condenserlens array 104, a beam switching module 203 including beamlet blankerarray 105, and projection optics module 204 including beam stop array108, beam deflector array 109, and projection lens arrays 110. Themodules are designed to slide in and out from an alignment frame. In theembodiment shown in FIG. 2, the alignment frame comprises an alignmentinner subframe 205 and an alignment outer subframe 206. A frame 208supports the alignment subframes 205 and 206 via vibration dampingmounts 207. The substrate 130 rests on substrate support structure 209,which is in turn placed on a chuck 210. The chuck 210 sits on the stageshort stroke 211 and long stroke 212. The lithography machine isenclosed in vacuum chamber 240, which may include a mu metal shieldinglayer or layers 215. The machine rests on base plate 220 supported byframe members 221.

Each module requires a large number of electrical signals and/or opticalsignals, and electrical power for its operation. The modules inside thevacuum chamber 240 receive these signals from control systems which aretypically located outside of the chamber 240. The vacuum chamber 240includes openings, referred to as ports, for admitting cables carryingthe signals from the control systems into the vacuum housing whilemaintaining a vacuum seal around the cables. Each module preferably hasits collection of electrical, optical, and/or power cabling connectionsrouted through one or more ports dedicated to that module. This enablesthe cables for a particular module to be disconnected, removed, andreplaced without disturbing cables for any of the other modules.

FIG. 3 a shows a top view of a layout of lithography system 300comprising a group of lithography system units according to anembodiment of the invention. Hereinafter, the layout may be referred toas lithography system 300 or cluster 300. FIG. 3 b schematically shows across-sectional side view of a portion of the lithography system 300.

In this particular embodiment, the lithography system 300 comprises agroup of ten lithography system units. The lithography system units arearranged back-to-back in two rows of five. Directly adjacent to thecluster 300, floor space is reserved as service area 305. Eachlithography system unit comprises a lithography apparatus 301 that iscontained in its own vacuum chamber, with one side of each vacuumchamber facing a lithography system unit in the other row, while theopposing side faces the surroundings of the cluster 300, in particularthe service area 305.

In case of a charged particle lithography apparatus, the vacuum chamberpreferably comprises all elements that enable lithography processing,including a charged particle source, a projector system for projectingcharged particle beamlets onto a substrate to be patterned, and amoveable substrate stage. For example, the vacuum chamber may correspondto the chamber 240 discussed with reference to FIG. 2.

The side of the lithography system unit facing a free area provided forservice purposes comprises a load lock system 310 for transferringsubstrates into and out of the vacuum chamber, and also comprises anaccess door 330 that can be opened for such service purposes.

The lithography system units are provided with a door 330 at the sameside as the load lock system 310. The door 330 may be removablyattachable, and may be removable in its entirety, for example by using atransfer unit 340. The transfer unit 340 may be arranged to support thedoor 330 and may comprise one or more transfer elements 345, such aswheels or rails. The lithography apparatus 301 may be supported by asupporting structure 335 for positioning the lithography apparatus at anelevated position.

The free area at the side at which the load lock system and access doorare located preferably is sufficiently large to accommodate thefootprint of the door and the load lock. Furthermore, it is desirablethat the free area is sufficiently large to accommodate a footprint ofan arrangement for carrying components of the lithography apparatus.

The lithography system 300 thus comprises a plurality of lithographysystem units having a load lock system 310 and a door 330 facing thesurroundings, more in particular facing the service area 305 surroundingthe lithography system 300. Due to the “outward” orientation of the loadlock systems 310 and doors 330, the lithography system units, includingthe lithography apparatuses 301 within the vacuum chambers, are directlyaccessible from the service area 305. Direct access simplifies servicingof the lithography system 300, and may reduce the downtime of thelithography system or parts thereof. Opening a single specific vacuumchamber for servicing can be done without affecting the throughput ofother lithographic system units within the lithography system 300.

The back-to-back layout of the lithography system units provides alithography system 300 with a limited “footprint”. Floor space within afab is valuable, and efficient use of the fab floor space is thusimportant.

The load lock system 310 may be integrated into the door 330.Integration of the load lock system 310 and the door 330 reduces theamount of material used in manufacturing the lithography system unit. Aportion of the door 330 may be directly used as one of the side walls ofthe load lock system 310. The material reduction has the advantage thatthe door and load lock system combination is easier to handle duringservicing. Furthermore, as less material is needed during manufacturing,the costs of manufacturing the lithography system are reduced as well.

The lithography system 300 further comprises a substrate supply system315. The substrate supply system 315 is arranged to receive substratesto be processed by the lithography system 300, and to provide thesesubstrates to the lithography system units for processing. This caneffectively mean that the substrate supply system 315 provides thesubstrates to a preparation system 320 for pre-processing purposes.After patterning, the substrate supply system 315 may collect thepatterned substrates. The use of a substrate supply system 315 enablesthe lithography system 300 to efficiently cooperate with other equipmentin the fab as it allows for a relatively easy replacement of presentlyused lithography systems.

FIG. 3 c schematically shows another side view of the lithography system300 of FIG. 3 a. In the shown embodiment, the lithography system 300further comprises a substrate transfer system 350 for receivingsubstrates from and/or sending substrates to the substrate supply system315. The substrate transfer system 350 may take the form of a suitableconveyor system, for example a conveyor system which extends in asubstantially horizontal direction.

Preferably, the substrate transfer system 350 is designed not tointerfere with the doors 330 of the lithography system units. This maybe accomplished as shown in FIG. 3 c. In this embodiment the substratetransfer system 350 extends in a substantially horizontal direction, andis arranged above the load lock systems 310, as well as the preparationunits 320, of the lithography system units. As a result, the door of asingle lithography system unit within the lithography system 300 may beopened for servicing purposes while the substrate transfer system 350can continue with the transfer of substrates between the substratesupply system 315 and the other lithography system units within thelithography system 300.

The layout described with reference to FIGS. 3 a-3 c provides a clusterof lithography system units with limited complexity. The layout can bescaled rather easily. For example, if the lithography system 300 needsto operate with an 80% capacity, only eight out of the ten lithographysystem units need to be operational and/or installed.

Furthermore, the lithography system 300 can provide a reliablethroughput. If one lithography system unit malfunctions and/or needsservicing, the other lithography system units within the cluster 300 maycontinue their operation. As a result, in case of 10 lithography systemunits with a throughput of 10 substrates, or wafers, per hour (wph),malfunctioning of one lithography system unit allows the cluster 300 tocontinue to work with a 90% efficiency. That is, it then operates with athroughput of 9×10 wph=90 wph instead of the ideal 100 wph. Incomparison, a state of the art optical lithography apparatus may operatewith a throughput of 100 wph. However, if some component within suchoptical lithography apparatus malfunctions, the entire apparatus needsto be shut down, reducing the throughput to 0 wph.

Before entry into the vacuum chamber, a substrate typically undergoesthe actions of clamping, pre-alignment and pump down. In this context,clamping is defined as providing a substrate on a substrate supportstructure to form a single structure, hereafter referred to as “clamp”.Furthermore, the term “clamped substrate” is used to refer to asubstrate being clamped to a substrate support structure. Pre-alignmentrelates to aligning the substrate and/or clamp such that patterning canbe performed onto a predetermined portion of the substrate in a certainorientation. Pump down relates to the step of reducing the pressuresurrounding the substrate to minimize contamination and to reduce theinfluence of the substrate on the vacuum chamber pressure upon insertioninto the lithography apparatus 301.

After the patterning action performed by the lithography apparatus 301,the substrate is typically exposed to a venting action, and anunclamping action, i.e. separating the substrate from the substratesupport structure. In between the venting and unclamping actions, thesubstrate may be transferred.

The load lock system 310 forms an interface to a vacuum environmentwithin the vacuum chamber. The system 310 is typically used for the pumpdown action and the venting action described above. For this purpose,the load lock system 310 comprises one or more chambers in which thepressure can be regulated. The load lock system 310 may comprise asingle chamber suitable for both pump down and venting actions.Alternatively the system 310 comprises separate chambers for pump downand venting. For the pump down action the system 310 comprises pumps forpumping down the pressure within a chamber to a reduced pressure, e.g. avacuum suitable for transfer of the clamped substrate and substratesupport to the lithographic apparatus 301. For the venting action theload lock system 310 comprises vents for venting a chamber to increasethe pressure after processing of the clamped substrate in thelithographic apparatus 301.

Clamping and/or unclamping may be performed in the preparation systems320. Alternatively, the clamping may be performed at a differentlocation prior to providing the substrate to the preparation systems320, for example within the common supply system 315. In yet anotheralternative, clamping and/or unclamping may be performed within the loadlock system 310.

Clamping and unclamping may be performed in separate units, but may alsobe executed in the same unit. Hereinafter the expression “clamping unit”refers to a unit for clamping and/or unclamping.

FIG. 4 schematically shows a lithography system unit provided with afirst load lock chamber 310 a for pump down, a second load lock chamber310 b for venting and a preparation system 320 that includes a number ofsubstrate preparation units 360 a-360 d. In this embodiment, a clamp isformed in a suitable substrate preparation unit 360 a-360 d in thepreparation system 320 and then inserted into the vacuum chamber via thefirst load lock chamber 310 a. After patterning of the substrate by thelithography apparatus 301, the clamp is transferred back to a suitablesubstrate preparation unit 360 a-d in the preparation system 320 via thesecond load lock chamber 310 b for unclamping.

As shown in the embodiment of FIG. 4, the preparation system 320 mayfurther include a pre-alignment unit 370 for pre-aligning the substratebefore entry into the lithography apparatus 301 via the first load lockchamber 310 a. Pre-alignment may be needed to ensure that the positionand/or orientation of the substrate on the substrate support structureare suitable for accurate exposure within the lithography apparatus 301.After pre-alignment in the pre-alignment unit 370 the substrate isprovided to the first load lock chamber 310 a for further processing.

Pre-alignment may be performed on an individual substrate before thesubstrate is clamped. In such case the pre-alignment may be done withina substrate preparation unit 360 a-360 d, which would reduce the spacebeing occupied by the lithography system unit. In case the substrate ispre-aligned in a separate pre-alignment unit 370 the substrate ispreferably pre-aligned while being clamped onto a substrate supportstructure. Pre-alignment of the clamped substrate reduces the requiredaccuracy at which the substrate is clamped onto the substrate supportstructure.

A preparation system 320 may further comprise one or more additionalunits. For example, the preparation system 320 may include aconditioning unit for conditioning clamped substrates and/or unclampedsubstrates prior to exposure in the lithography apparatus 301. Theconditioning unit may be arranged for thermal conditioning of a clampedor unclamped substrate by e.g. removing heat energy from the substrate(and substrate support structure) to improve the accuracy oflithographic patterning, as is known to persons skilled in the art.

Substrates and/or clamps may be transferred between different units byusing a robot that operates within a robot space 400. In the exemplaryembodiment of FIG. 4 the robot comprises a carrier 401 that can move ina substantially vertical direction. Therefore, such robot will hereafterbe referred to as vertical transfer robot or VTR. The carrier 401 isarranged for suitably transporting substrates and/or clamps between theload lock chambers 310 a, 310 b, the substrate preparation units 360a-360 d, and the pre-alignment unit 370. In addition, the robot 401 mayfurther be arranged to handle substrate exchange with the substratetransfer system 350. In FIG. 4 the carrier 401 carries a clampcomprising a substrate support structure 403 with a substrate 405clamped thereon.

A lithography system unit may further comprise a storage unit 410 fortemporarily storing substrates. The stored substrate may be substratesthat still need to be patterned by the lithography apparatus 301.Alternatively or additionally, the substrate storage unit 410 may bearranged to store patterned substrates awaiting transfer via thesubstrate transfer system 350. In the embodiment shown in FIG. 4, thestorage unit 410 is coupled to the substrate transfer system 350.Alternatively, or additionally, the storage unit 410 may be coupled to areplaceable unit and may take the form of a so-called front openingunified pod (FOUP). FOUPs enable relatively safe transfer of severalsubstrates in one FOUP in a (clean room) environment. In yet anotherembodiment, the storage unit 410 is a replaceable unit, for example aFOUP.

Additionally, FIG. 4 schematically shows that electronics 420 needed toensure proper operation of the lithography apparatus 420 may be placedon top of the lithography apparatus 301. Just like the embodiment shownin FIG. 3 b, the door 330 can be removed together with the othercomponents outside the vacuum chamber, for example by means of atransfer unit 340 comprising one or more transfer elements 345.

Although different components in FIG. 4 are shown on top of each other,alternative embodiments in which one or more of the components arepositioned adjacent to each other in a substantially horizontaldirection are envisioned as well. Furthermore, the order of thedifferent components may be different.

In other embodiments of the lithography system, not shown in FIG. 4,clamping and/or unclamping is performed within the load lock system 310.Load lock systems 310 that are capable of executing these actions thenneed to be rather sophisticated in nature.

Clamping methods include but are not limited to clamping by usingcapillary forces, for example as described in US patent application2010/0265486 assigned to the owner of the present invention and herebyincorporated by reference in its entirety. Clamping by applying avacuum, clamping by freezing the substrate to the substrate supportstructure, and clamping by the use of electromagnetic forces are some ofthe possible alternatives. The type of clamping may depend on the typeof subsequent processing to be used on the substrate.

The load lock systems 310 a, 310 b, as well as other units within thelithography system, for example one or more units in the preparationsystems 320, such as pre-alignment units 370, clamping/unclamping units360 and substrate storage systems 410 may comprise one or more valvesfor creating a controlled pressure environment. Keeping the substratesand/or clamps in a controlled pressure environment permits a reducedcontamination environment to be maintained around the substrates. Thecontrolled pressure environment may be an intermediate vacuum, betweenatmospheric pressure and the high vacuum of the lithography apparatus301. This intermediate vacuum enables a reduction of contamination whileavoiding having a large volume maintained at a high vacuum. Inparticular in case of not yet patterned substrates the intermediatevacuum aids in preparing the substrate for later processing in thevacuum environment of the lithography apparatus.

A lithography system where the clamping and/or unclamping units areprovided within the lithography system units, for example within apreparation system 320 as shown in FIG. 4 or within a load lock system310, may be identified as a clustered lithography system 300 with alocalized unclamped substrate supply or “localized cluster”. In alocalized cluster unclamped substrates are transported to an area inclose proximity of the lithography apparatus 301 in which they are to beprocessed. Then, the substrates are clamped on a substrate supportstructure, and finally the clamps, i.e. substrates clamped onto asubstrate support structure, are provided to the lithography apparatus301. Because not many components are shared between the differentlithography system units, localized clusters can be scaled relativelyeasy, as addition and/or removal of a lithography system unit merelymeans that, at most, adjustments have to be made to way substrates areprovided.

FIG. 5 schematically shows an action flow for processing a substrate ina lithography system unit. Transfer of the substrate may be accomplishedusing a substrate handling robot, FIG. 5 illustrating the trajectory ofthe robot for making the sequence of transfers. The robot may compriseand/or take the form of a carrier such as carrier 401 in FIG. 4. In FIG.5, the interface between the substrate transfer system and the robot isdenoted by “IF”. Furthermore, the exemplary lithography system unitcomprises a storage unit SU, a first preparation system unit PSU-1, asecond preparation system unit PSU-2, and a load-lock LL coupled to alithography apparatus.

As mentioned earlier, the interface IF may correspond to the interfacebetween the substrate transfer system 350 and the lithography systemunit described above with reference to FIG. 4. The storage unit SU maycorrespond to the storage unit 410 described above with reference toFIG. 4. The preparation units PSU-1 and PSU-2 may for example comprisetwo of the substrate preparation units 360 described above. Finally, theload lock LL may correspond to the load lock system 310 described abovewith reference to FIG. 4. Alternatively, the load lock LL may comprisesa single load lock chamber comprising one or more carriers to enable thehandling of more than one substrate in the load lock LL. Movementsduring which the robot actually transfers a substrate are represented bythe solid arrows. Mere movements of the robot without substrate transferare denoted by the dashed arrows.

The trajectory in FIG. 5 starts with the robot being positioned at theinterface IF. The first movement involves the transfer of a newunclamped substrate to be exposed from the interface IF towards thestorage unit SU for temporary storage in action 501. Note that prior tosuch transfer in action 501 the substrate may have been aligned in arelatively coarse manner, for example by detection of the orientation ofa substrate notch or the like. After placement of the substrate in thestorage unit SU, the robot moves towards the first preparation systemunit PSU-1 in action 502. At preparation system unit PSU-1, the robotpicks up an exposed unclamped substrate and transfers this substrate inaction 503 to the interface IF to allow removal thereof from thelithography system unit. The robot then moves back in action 504 tostorage unit SU to pick up the unclamped substrate for exposure placedtherein at the end of action 501. In action 505, the unclamped substrateis picked up from the storage unit SU and transferred to the preparationsystem unit PSU-1. After placement of the unclamped substrate in thePSU-1, the robot moves in action 506 to the preparation system unitPSU-2. The robot then picks up a clamped substrate to be exposed andtransfers the clamped substrate to the load lock LL for exposure in thelithography apparatus in action 507. After removal of the clampedsubstrate at the load lock, the robot picks up an exposed clampedsubstrate and transfers this substrate to preparation system unit PSU-2for unclamping in action 508. Finally, the robot moves to the interfaceIF without carrying a substrate in action 509. The series of actions501-509 is referred to as “cycle A”.

The trajectory in FIG. 5 then continues at the interface IF with action511, which is similar to action 501. However, after placement of the newunclamped substrate to be exposed, the robot does not move topreparation system unit PSU-1 as in action 502, but instead moves topreparation system unit PSU-2 in action 512. Subsequently, in action513, the robot picks up an exposed clamped substrate present inpreparation system unit PSU-2, and transfers this substrate to theinterface IF to enable removal of the substrate from the lithographysystem unit. The robot then moves to the storage unit SU in action 514in a similar fashion as it did in action 504. The robot then picks up anunclamped substrate to be exposed from the storage unit SU and transfersthis substrate to the preparation system unit PSU-2 in action 515. Afterdelivery of this unclamped substrate, the robot moves to the preparationsystem unit PSU-1 in action 516, picks up a clamped substrate to beexposed and transfers the clamped substrate to the load lock LL forexposure in the lithography apparatus in action 517. After removal ofthe clamped substrate at the load lock, the robot picks up an exposedclamped substrate and transfers this substrate to preparation systemunit PSU-1 for unclamping in action 518. Finally, the robot moves to theinterface IF without carrying a substrate in action 519. The series ofactions 511-519 is referred to as “cycle B”.

The robot may now repeat the trajectory of FIG. 5, which effectivelymeans that it alternates between following cycle A and cycle B, wherethe difference between the two cycles is the role of the preparationsystem unit PSU-1 and the preparation system unit PSU-2. The trajectoryshown in FIG. 5 is particularly useful to ensure a continuous flow ofsubstrates in case the clamping action in a preparation system unittakes more time than the duration of an entire cycle.

In view of the desire to have a lithography system of limited size, thestorage capacity of the components within the lithography system unit ispreferably limited. In particular, PSU-1 and PSU-2 are generally onlycapable of facilitating the preparation of a single substrate.Similarly, the storage unit SU preferably stores a single substrate. Theload lock LL is preferably capable of storing two substrates clampedonto corresponding substrate support structures. The possibility toaccommodate two clamped substrates in the load lock LL enables placementof a clamped substrate in the load lock LL without the need to firstremove a substrate that has been processed earlier. The load lock LL maycomprise a single load lock chamber. Alternatively, the load lock LLcomprises more than one load lock chamber, for example as described withreference to FIG. 4. In this multiple-chamber embodiment, each load lockchamber is preferably arranged to accommodate a single substrate clampedonto a substrate support structure.

In case only single substrates are stored in the storage unit SU, thepreparation system unit PSU-1 and the preparation system unit PSU-2, thefollowing could be said with respect to a wafer N that is processedfollowing the trajectory as described with reference to FIG. 5. Thewafer N would be transferred from the interface IF to the storage unitSU in action 501, optionally after the orientation of the wafer has beenchanged as a result of an alignment procedure at the interface IF. Thewafer N is then transferred to the first preparation system unit PSU-1in action 505. In case of the use of a storage unit SU with a capacityof a single wafer, the storage unit SU would thus then be empty. Thewafer N is then clamped and the clamped substrate is then transferred tothe load lock LL in accordance with action 517. Besides clamping, otheractions may also be performed in the preparation system unit PSU-1. Forexample, relatively fine alignment, in particular with respect to theorientation of the wafer N with respect to the substrate supportstructure onto which the wafer N is to be clamped, may be executed abrief period of time prior to clamping. Via the load lock LL the wafer Nis transferred into the lithography apparatus for lithographic exposure.Within the lithography apparatus one or more further actions may beperformed prior to exposure. Such actions may include one or moremeasurements such as alignment mark measurement, beam positioningmeasurement, and beam current measurement. Actions related to suchmeasurement may include, but are not limited to movement of the wafer Nto a focal plane sensor, measure global orientations in differentdirections such as x, y, z, Rx, Ry and Rz, scan marks around fields onthe wafer N, movement of the wafer N to marks, such as knife edgealignment marks, on an alignment sensor, and movement of the wafer N toa beam positioning sensor. After exposure, the wafer N is transferredback to the load lock chamber LL and removed by the robot andtransferred to a preparation system unit for unclamping corresponding toaction 508 or action 518 depending on the preparation system unit thatis being used. Finally, the wafer N is moved to the interface in action509 or action 519 to enable removal of the processed wafer N from thelithography system unit by the substrate transfer system.

In the scenario described above, the wafer that is to be processed afterwafer N, i.e. wafer N+1, occupies the place left open by wafer N in thestorage unit SU as a result of the robot transferring wafer N+1 from theinterface IF to the storage unit SU in action 511. The substrate is thenmoved to the preparation system unit PSU-2 in action 515. Afterpreparation, the wafer N+1 is transferred to the load lock LL.Preferably, at this time, wafer N is also present in the load lock LL,ready to be removed from the load lock, and to be transferred topreparation system unit PSU-2 by the robot in action 508. In suchscenario, wafer N would thus effectively takes the place previouslyoccupied by wafer N+1 in the preparation system unit PSU-2.

In the scenario described above, the wafer that is processed prior towafer N, i.e. wafer N−1, is the wafer that resides in the load lock LLwhen wafer N is placed therein as a result of action 517. Wafer N−1 isthen removed from the load lock LL and transferred to the substratepreparation unit PSU-1 in action 518 to take the place previouslyoccupied by wafer N.

FIG. 6 shows a perspective view of a lithography system 300. In suchlithography system 300 all components may be protected from the outsideenvironment by means of a suitable housing or casing 600. The housing600 includes removable portions, or may be removable in its entirety, tofacilitate maintenance, repair, and operational adjustment of componentswithin the lithography system 300. The housing 600 may be provided withone or more interfaces that allow operators to monitor and/or adjustparameters within the lithography system 300. The interfaces maycomprise a display 610 and/or a keyboard 620 for these purposes.

FIG. 7 shows a portion of the clustered lithography system of FIG. 6with a portion of its cover being removed. FIG. 7 shows elements usedfor transfer and preparation of substrate for five lithography systemunits. The substrates are provided via the substrate transfer system 350comprising a transfer robot 650 that moves in a substantially horizontaldirection, hereafter referred to as horizontal transfer robot or HTR650. The HTR 650 is arranged to transfer substrates to be processedtowards a lithography system unit and to transfer processed substrateaway from a lithography system unit. An exchange of substrates betweenthe substrate transfer system 350 and the lithography system unit isperformed via an interface 640.

Each lithography system unit is further provided with at least twosubstrate preparation units 360, a storage unit 410 and a load lock 310arranged for accommodation of at least two substrates or clamps. Thelithography system unit further includes a carrier 401 for movingsubstrates and/or clamps between the different units, for examplefollowing a trajectory as discussed with reference to FIG. 5. Since thecarrier 401 will move in a substantially vertical direction, hereafterthe carrier may be referred to as vertical transfer robot or VTR 401.

FIGS. 8 a, 8 b provide a more detailed view of the interface 640 betweenthe substrate transfer system 350 and a lithography system unit atdifferent stages of substrate transfer. The interface 640 comprises achamber 641 provided with a top wall provided with an opening 642 thatis sufficiently large to allow a substrate 405 to be transferred throughthe opening 642. The chamber 641 further includes a supporting surface643 and at least three extendible pins 644. The at least threeextendible pins 644 are positioned in the supporting surface 643 and canmove in a substantially vertical direction. The pins 644 are placed withrespect to each other in such a way that they can support a substrate405 in a stable manner. Furthermore, the pins 644 are positioned in away that they do not interfere with HTR 650 and VTR 401 so that theserobots may transfer the substrate 405 without being hindered by the pins644.

The HTR 650 comprises a body 651 that can move along a guiding rail 652.The body 651 is provided with two opposing support units 653 that may beprovided with one or more extensions or “fingers”. The two opposingsupport units 653 are arranged for holding the substrate 405 in a stableposition. The HTR 650 is constructed in such a way that its componentsdo not interfere with the pins 644 while being positioned at the edge ofthe opening 641 to enable substrate transfer between the HTR 650 and thelithography system unit.

Supply of a substrate 405 to a lithography system unit may be performedin the following way. First the HTR 650 is provided with a substrate 405that rests on top of the supporting units 653. The HTR 650 thentransfers the substrate 405 by movement of the body 651 in asubstantially horizontal direction along a guiding rail 652 until thesubstrate 405 is positioned above the opening 461. It will be understoodthat the HTR 650 can take many different forms and the means of movingthe HTR 650 may well be different from the way depicted in FIGS. 8 a, 8b. Subsequently, the pins 644 will move upward through the hole untilthey engage with the substrate 405. At that point the pins 644 will moveupwards somewhat further to lift the substrate 405 from the supportingunits 653 of the HTR 650. The HTR 650 is then moved away from theopening 641 as depicted in FIG. 8 b. Finally, the pins 644 are loweredsuch that the substrate 405 enters the interface chamber 461. The endposition of the pins 644 is determined by the specific size and shape ofthe VTR 401 that is used in the lithography system unit. Removal of asubstrate 405 from a lithography system unit may be performed byperforming the actions described above in a reverse order.

FIGS. 9 a, 9 b schematically show a carrier 401 according to anembodiment of the invention. The carrier 401 comprises a body 680provided on a robot arm comprising a base 681 a that can be moved alonga rail 683, the rail being oriented in a substantially verticaldirection. The robot arm 681 further comprises different sections 681 b,681 c, which enable the arm to translate and rotate the substrate in atwo-dimensional plane, typically the substantially horizontal plane. Thebody 680 is provided with at least two extended portions or fingers 684a, 684 b for carrying a substrate 405. Additionally, the body 680 isprovided with at least two further extended portions or fingers 685 a,685 b for carrying a substrate support structure 403 onto which asubstrate 405 may be clamped. Preferably, the fingers 684 a, 684 b forcarrying a substrate 403 are positioned at a level below the fingers 685a, 685 b. Preferably, the difference in height exceeds the thickness ofthe substrate support structure 403 to ensure that the fingers 684 a,684 b do not hamper the carrying performance of the fingers 685 a, 695b. In an optimal design, the fingers 684 a, 684 b may provide additionalsupport in case a clamp is being transferred by the carrier 401.

The fingers 684 a, 684 b preferably extend in a single direction, i.e.they take the form of straight bars. Most preferably, the fingers 684 a,684 b extend in directions substantially parallel to each other. Thefingers 685 a, 685 b preferably have an arched or crescent shape, theends of the fingers 685 a, 685 b opposing each other. Both the fingers684 a, 684 b and 685 a, 685 b have a length that is sufficiently long toextend underneath more than halfway the structure they are designed tosupport. In case of a circular shape, such length should thus exceed theradius of the structure to be carried.

The VTR 401 takes the substrate from the interface chamber 641 asdiscussed with reference to FIGS. 8 a, 8 b and transfers the substrate405 to a substrate preparation unit 360 or storage unit 410. In thelatter case, as depicted in FIG. 10 by means of the dashed arrow, theVTR 401 transfers the substrate 405 from the substrate unit 410 to thesubstrate preparation unit 360 to enable clamping onto a substratesupport structure and to perform other suitable preparation actions. Thestorage unit 410 comprises a supporting surface 411 and may include pins414 that may be extended in a substantially vertical direction. In caseof insertion or removal of a substrate the pins 414 are suitablyextended to allow the fingers 684 a, 684 b that support the substrate405 to slide past at least some of the pins 414 at a height lower thanthe pin ends. When the fingers 684 a, 684 b are in the correct position,i.e. prior to insertion such that the substrate 405 supported by thefingers 684 a, 684 b is suitably placed above the pins 414, and prior toremoval such that the fingers 648 a, 684 b are suitably placedunderneath the substrate 405 supported by the pins 414, the pins 414move to allow transfer from the substrate 405 between the pins 414 andthe fingers 684 a, 684 b.

In case of insertion, the pins 414 then move upwards until they are insufficient contact with the substrate 405. At that stage, either thepins 414 move upwards somewhat further or the VTR 401 is moved downwardsto separate the substrate 405 from the VTR 401, and allow the support ofthe substrate 405 to be entirely taken over by the pins 414. Aftersufficient separation, the VTR 401 is retracted out of the storage unit410.

In case of substrate removal, the pins 414 move downwards until thefingers 684 a, 684 b of the VTR 401 are in sufficient contact with thesubstrate 405. At that stage, either the VTR moves upwards or the pins414 are moved downwards to separate the substrate 405 from the pins 414and allow the support of the substrate 405 to be entirely taken over bythe VTR 401. After sufficient separation, the VTR 401 is retracted outof the storage unit 410.

FIG. 11 shows a substrate preparation unit 360 in which a substratesupport structure 403 is placed onto which a substrate 405 is to beclamped. The substrate is supported on pins 364 that operate in asimilar way as pins 414 discussed with reference to FIG. 10. Preferably,the substrate support structure 403 is provided with notches 361 thatenable accommodation of the pins 364 within the substantially circularcircumference of the substrate support structure 403 that would havebeen formed if such notches 361 would have been absent. The use ofnotches 361 limits the space that is occupied by the combination ofsubstrate support structure 403 and pins 364. Furthermore, by allowingthe pins 364 to extend through the notches 361 the substrate 405, whenclamped onto the substrate support structure 403, is in contact with thesupport structure 403 over a larger area which may improve the clampingquality. Finally, the use of notches in the substrate support structuremay enable some form of coarse pre-alignment.

Clamping methods include but are not limited to clamping by usingcapillary forces, for example as described in US patent application2010/0265486 assigned to the owner of the present invention and herebyincorporated by reference in its entirety. Clamping by applying avacuum, clamping by freezing the substrate 405 to the substrate supportstructure 403, and clamping by the use of electromagnetic forces aresome of the possible alternatives. The type of clamping may depend onthe type of subsequent processing to be used on the substrate 405. Thesupply of fluids, for example in case of clamping by using capillaryforces, or removal of air, for example in case of clamping by applying avacuum, may be executed via one or more tubes 365. The surface of thesubstrate support structure 403 for receiving the substrate 405 may beprovided with a pattern of grooves and/or other elevated structures suchas burls, to enhance the clamping process.

The substrate support structure 403 is further provided with a number ofprotrusions or lips 362. These lips 362 are positioned along thecircumference of the substrate support structure 403. The lips 362 areused to engage with the fingers 685 a, 685 b of the VTR 401. In FIG. 11,the lips 362 are located at a height level that is close to the surfaceof the substrate support structure 403 onto which the substrate 405 isto be clamped. To enhance the stability during transfer the lips 362 arepreferably located above the center of mass of the substrate supportstructure 403, and preferably also above the center of mass of thecombination of a substrate support structure 403 and a substrate 405clamped thereon. In some embodiments, another lip 362 may be used toengage with the body 680 of the VTR 401.

In some embodiments, such as the embodiment shown in FIG. 11, thesubstrate support structure 403 is provided with further protrusions orlips 363, 366. The at least two lips 366 (only one lip is depicted inFIG. 11) are provided at the same height level as the lips 362. The lip633 is provided at a lower height level. In the embodiment discussedhereafter, these lips 363, 366 are used by a handling robot in the loadlock system 310.

Preferably, the lips 362 used to engage with the VTR fingers 685 a, 685b are located along one side of the substrate support structure 403,that side being the side facing away from the VTR body 680. Sucharrangement reduces the risk of tilt or tipping over during transfer.

In embodiments using the at least two lips 366 and at least one lip 363,the at least two lips 366 are preferably located between the lips 362used to engage with the VTR fingers 685 a, 685 b. The at least one lip363 is located at the side facing the VTR body 680.

FIG. 12 schematically shows a clamped substrate handling robot for usein a load lock system 310. The handling robot receives clampedsubstrates to be processed from the VTR 401 via passage 710 andtransfers the clamped substrate towards the lithography apparatus viapassage 705 in door 330. Similarly, the handling robot receivesprocessed clamped substrates from the lithography apparatus via passage705 and hands over the substrate to the VTR 401 entering via passage710.

The handling robot comprises a body 701 provided on a robot arm. Thebody 701 is provided with at least two extended portions or fingers 702a, 702 b for carrying a substrate support structure 403 onto which asubstrate 405 is clamped. Preferably, the fingers 702 a, 702 b have anarched or crescent shape, and have a length that is sufficiently long toextend underneath more than halfway the structure they are designed tosupport. The finger 702 a has a different, i.e. higher, height levelthan the finger 702 b. The reason for this difference in height levelwill be discussed with reference to FIG. 13 b.

FIG. 13 a shows the transfer of the clamped substrate from the substratepreparation unit 360 towards the load lock system 310. The load locksystem 310 comprises a clamped substrate handling robot comprising arobot arm 720 onto which two handling bodies 701 a, 701 b are attachedabove each other.

FIG. 13 b shows a more detailed view of the load lock system 310 at atime just after delivery of the clamped substrate to the upper handlingbody 701 a. In FIG. 13 b, merely a portion of the robot arm 720 isshown, i.e. the portion that relates to the upper handling body 701 a.The robot arm 720 comprises a base 721 a that can be moved along a rail721 c, the rail 721 c being oriented in a substantially verticaldirection. The robot arm 720 further comprises different sections 721 b,connected to the base 721 a and the body 701 a, that enables the arm totranslate and rotate the clamp that is being held by the fingers 702 a,702 b in a two-dimensional plane.

In the embodiment shown in FIG. 13 b, the substrate support structure403 is provided with lips 362 have been used to engage with the VTRfingers 685 a, 685 b located along a side of the substrate supportstructure 403 facing away from the VTR body 680 (the left side in FIG.13 b). Furthermore, an additional lip 362 located on the other side ofthe substrate support structure 403 have been used to engage with theVTR body 680. Furthermore, two lips 366 (only one shown) are used toengage with the upper finger 702 a extending from the upper body 701 aof the handling robot and the lip 363 is used to engage with the lowerfinger 702 b extending from the upper body 701 a of the handling robotsuch that the upper body 701 a is able to independently carry thesubstrate support structure 403. The position of the fingers 702 a, 702b (one high, one low) in combination with the different orientation ofthe two sets of fingers 702 a, 702 b, and 685 a, 685 b with respect toeach other (i.e. at an angle) allows both sets of fingers to hold thesubstrate support structure simultaneously without interfering with eachother. As a result, if one of the sets of fingers is retracted, thesubstrate support structure 403 will be held by the other set offingers. The design of the respective handling robots, i.e. VTR 401 andclamped substrate handling robot in load lock system 310, makes itpossible to hand over a substrate support structure 403 in a direct way.Such handover reduces the space that is needed for substrate supportstructure transfer, which helps to keep the size of the lithographysystem unit as small as possible.

FIGS. 14 a, 14 b schematically show the transfer of a processed clampedsubstrate from the load lock system 310 towards a substrate preparationunit 360 by means of the VTR 401 (see dashed line). In FIG. 14 a, theVTR 401 picks up the clamped substrate after handover with the lowerhandling body 701 b of the handling robot. In FIG. 14 b, the VTR 401places the clamped substrate in the substrate preparation unit 360 forunclamping.

The empty space left in the load lock system 310 may now be occupied bya processed clamp that is received from the lithography apparatus asshown in FIG. 15 a. The clamped substrate to be processed that wasrecently put in (see FIG. 13 b), may then be inserted into thelithography apparatus for processing as shown in FIG. 15 b.

Alternatively, the clamped substrate to be processed (held by upper body701 a) is entered into the lithography apparatus after removal of theprocessed clamped substrate. In such case, the lower body 701 b may nothold any clamped substrate until a new clamped substrate to be processedis provided by the VTR 401 or until the clamped substrate recently putin the lithography apparatus has been processed.

Although some embodiments of the invention have been described withreference to a lithography system comprising ten lithography systemunits, the number of lithography system units within a lithographysystem may vary. For example, instead of ten lithography system units,any other number of lithography system units above one may be used.

The invention has been described by reference to certain embodimentsdiscussed above. It will be recognized that these embodiments aresusceptible to various modifications and alternative forms well known tothose of skill in the art without departing from the spirit and scope ofthe invention. Accordingly, although specific embodiments have beendescribed, these are examples only and are not limiting upon the scopeof the invention, which is defined in the accompanying claims.

1. An apparatus for transferring substrates within a lithography system,the lithography system comprising an interface with a substrate supplysystem for receiving unclamped substrates and a substrate preparationunit for clamping an unclamped substrate onto a substrate supportstructure to form a clamped substrate; wherein the apparatus comprises abody provided with a first set of fingers for carrying an unclampedsubstrate and a second set of fingers for carrying a clamped substrate;and wherein the first set of fingers is located below the second set offingers, and fingers of the first set of fingers have a different shapethan the fingers of the second set of fingers.
 2. The apparatus of claim1, wherein the fingers of the first and second sets of fingers bothextend from the body in the same direction, and the fingers of the firstset of fingers are arranged sufficiently below the fingers of the secondset of fingers so that the fingers of the first set of fingers do notinterfere with a substrate support structure carried by the second setof fingers.
 3. The apparatus of claim 1, wherein the fingers of thefirst set of fingers takes the form of straight, substantially parallelbars, with a length extending from the body that exceeds the radius ofthe unclamped substrate.
 4. The apparatus of claim 1, wherein thefingers of the second set of fingers take the form of opposingcrescent-shaped structures with a length extending from the body thatexceeds the radius of the substrate support structure.
 5. The apparatusof claim 4, wherein the fingers of the second set of fingers arearranged to surround, at least partially, the substrate supportstructure.
 6. The apparatus of claim 1, wherein the body is mounted on arobot arm comprising a base moveable in a substantially verticaldirection, and one or more sections for movement in a substantiallyhorizontal plane.
 7. The apparatus of claim 6, wherein the apparatus isarranged for transferring both unclamped and clamped substrates betweena plurality of locations arranged at different heights, the base beingarranged for vertical movement within a robot space, and the robot armbeing arranged for transferring the unclamped and clamped substrateshorizontally between the locations at different heights and the robotspace to transfer the substrates between the locations.
 8. The apparatusof claim 7, further comprising a horizontal transfer apparatus arrangedfor transferring unclamped substrates to and from the interface.
 9. Theapparatus of claim 8, wherein the interface comprises three or morepins, the pins arranged for vertical movement to lift an unclampedsubstrate from a first position accessible by the first set of fingersof the substrate transfer apparatus to a second position accessible bythe horizontal transfer apparatus.
 10. A load lock transfer apparatusfor transferring substrate support structures onto which substrates havebeen clamped within a load lock system in a lithography system unit;wherein the apparatus comprises a body provided with at least twofingers for carrying the substrate support structure; and wherein atleast two of the fingers are arranged at different height levels. 11.The load lock transfer apparatus of claim 10, wherein the fingers takethe form of opposing crescent structures with a length extending fromthe body that exceeds the radius of the substrate support structure. 12.The load lock transfer apparatus of claim 10, wherein the fingers arearranged to surround, at least partially, the substrate supportstructure.
 13. A lithography system comprising: a lithography apparatusarranged in a vacuum chamber for patterning a substrate; a load locksystem for transferring substrates into and out of the vacuum chamber; asubstrate preparation unit for clamping a substrate onto a substratesupport structure to form a clamped substrate; an interface with asubstrate supply system for receiving unclamped substrates; and asubstrate transfer apparatus for transferring substrates within thelithography system according to claim
 1. 14. The lithography system ofclaim 13, wherein the load lock system is provided with a load locktransfer apparatus according to claim 10, the load lock transferapparatus arranged for receiving substrate support structures from thesubstrate transfer apparatus and placing the substrate supportstructures into the lithography apparatus, and for removing substratesupport structures from the lithography apparatus and giving thesubstrate support structures to the substrate transfer apparatus.
 15. Asubstrate support structure for carrying a substrate for use in alithography system, according to claim 13, the substrate supportstructure comprising: a body provided with a surface for accommodatingthe substrate; and two protrusions positioned along the circumference ofthe substrate support structure, wherein the protrusions are located ata first height level above the center of mass of the substrate supportstructure.
 16. The substrate support structure of claim 15, wherein thefirst height level is above the center of mass of the combination of thesubstrate support structure and a substrate clamped thereon.
 17. Thesubstrate support structure of claim 15, wherein the two protrusions arelocated along one side of the substrate support structure.
 18. Thesubstrate support structure of claim 17, further comprising a furtherprotrusion located at the other, opposing, side of the substrate supportstructure.
 19. The substrate support structure of claim 17, wherein thestructure further comprises three additional protrusions, wherein two ofthe additional protrusions are provided at the first height levelbetween the two protrusions located along the one side of the substratesupport structure, and wherein the third protrusion of the additionalprotrusions is provided at the other, opposing, side of the substratesupport structure at a second height level, the second height levelbeing lower than the first height level.
 20. A method for handing over asubstrate support structure provided with a substrate on a surfacethereof, the substrate support structure comprising: a body providedwith a surface for accommodating the substrate; two or more firstprotrusions positioned around the circumference of the substrate supportstructure, at least one of the first protrusions being positioned at afirst height level above the center of mass of the substrate supportstructure; two or more second protrusions positioned around thecircumference of the substrate support structure, at least one of thesecond protrusions being positioned at a first height level above thecenter of mass of the substrate support structure and at least one ofthe second protrusions being positioned at a second height level lowerthan the first height level; the method comprising; picking up thesubstrate support structure with a substrate transfer apparatusaccording to claim 1, so that the fingers of the second set of fingersengage with the first protrusions; moving the substrate supportstructure towards a load lock transfer apparatus according to claim 8moving the substrate transfer apparatus or the load lock transferapparatus so that the fingers of the load lock transfer apparatus engagewith the second protrusions; and moving the substrate transfer apparatusor the load lock transfer apparatus so that the fingers of the substratetransfer apparatus disengage from the first protrusions; and retractingthe substrate transfer apparatus so that the substrate support structureis carried by the load lock transfer apparatus.
 21. The method of claim20, wherein the step of moving the substrate transfer apparatus or theload lock transfer apparatus so that the fingers of the load locktransfer apparatus engage with the second protrusions comprises movingthe substrate transfer apparatus or the load lock transfer apparatus sothat at least one of the fingers of the substrate transfer apparatus andat least one of the fingers of the load lock transfer apparatus overlapeach other at different heights around the circumference of thesubstrate support structure.